You could create a Repeater Field in Backend use the Export Tool to see how you can do it. A Repeater with a textfield looks like this.
if( function_exists('acf_add_local_field_group') ):
acf_add_local_field_group(array(
'key' => 'group_5c18f89ca825f',
'title' => 'repeater',
'fields' => array(
array(
'key' => 'field_5c18f8a29941c',
'label' => 'repeaterField',
'name' => 'repeaterFieldName',
'type' => 'repeater',
'instructions' => '',
'required' => 0,
'conditional_logic' => 0,
'wrapper' => array(
'width' => '',
'class' => '',
'id' => '',
),
'collapsed' => '',
'min' => 0,
'max' => 0,
'layout' => 'table',
'button_label' => '',
'sub_fields' => array(
array(
'key' => 'field_5c18f8ba9941d',
'label' => 'repeaterField-TextField',
'name' => 'repeaterfield-textfieldName',
'type' => 'text',
'instructions' => '',
'required' => 0,
'conditional_logic' => 0,
'wrapper' => array(
'width' => '',
'class' => '',
'id' => '',
),
'default_value' => '',
'placeholder' => '',
'prepend' => '',
'append' => '',
'maxlength' => '',
),
),
),
),
'location' => array(
array(
array(
'param' => 'post_type',
'operator' => '==',
'value' => 'post',
),
),
),
'menu_order' => 0,
'position' => 'normal',
'style' => 'default',
'label_placement' => 'top',
'instruction_placement' => 'label',
'hide_on_screen' => '',
'active' => 1,
'description' => '',
));
endif;
